In the wake of that resolution of accession, the "German reunification treaty",    commonly known in German as " Einigungsvertrag " (Unification Treaty) or " Wiedervereinigungsvertrag " (Reunification Treaty), that had been negotiated between the two German states since 2 July 1990, was signed by representatives of the two Governments on 31 August 1990. This Treaty, officially titled Vertrag zwischen der Bundesrepublik Deutschland und der Deutschen Demokratischen Republik über die Herstellung der Einheit Deutschlands (Treaty between the Federal Republic of Germany and the German Democratic Republic on the Establishment of German Unity), was approved by large majorities in the legislative chambers of both countries on 20 September 1990  (442–47 in the West German Bundestag and 299–80 in the East German Volkskammer). The Treaty passed the West German Bundesrat on the following day, 21 September 1990. The amendments to the Federal Republic's Basic Law that were foreseen in the Unification Treaty or necessary for its implementation were adopted by the Federal Statute of 23 September 1990, that enacted the incorporation of the Treaty as part of the Law of the Federal Republic of Germany. The said Federal Statute, containing the whole text of the Treaty and its Protocols as an annex, was published in the Bundesgesetzblatt (the official journal for the publication of the laws of the Federal Republic) on 28 September 1990.  In the German Democratic Republic, the constitutional law ( Verfassungsgesetz ) giving effect to the Treaty was also published on 28 September 1990.  With the adoption of the Treaty as part of its Constitution, East Germany legislated its own abolition as a State.
East Germany decided to upgrade the fortifications in the late 1960s to establish a "modern frontier" that would be far more difficult to cross. Barbed-wire fences were replaced with harder-to-climb expanded metal barriers; directional anti-personnel mines and anti-vehicle ditches blocked the movement of people and vehicles; tripwires and electric signals helped guards to detect escapees; all-weather patrol roads enabled rapid access to any point along the border; and wooden guard towers were replaced with prefabricated concrete towers and observation bunkers. 
In the Yalta and Potsdam conferences, the Allies established their joint military occupation and administration of Germany via the Allied Control Council (ACC), a four-power (US, UK, USSR, France) military government effective until the restoration of German sovereignty. In eastern Germany, the Soviet Occupation Zone (SBZ – Sowjetische Besatzungszone ) comprised the five states ( Länder ) of Mecklenburg-Vorpommern , Brandenburg , Saxony , Saxony-Anhalt , and Thuringia . Disagreements over the policies to be followed in the occupied zones quickly led to a breakdown in cooperation between the four powers, and the Soviets administered their zone without regard to the policies implemented in the other zones. The Soviets withdrew from the ACC in 1948; subsequently as the other three zones were increasingly unified and granted self-government, the Soviet administration instituted a separate socialist government in its zone.